(1) Field of the Invention
The present invention relates to a solvent-free, biodegradable cleaning composition having particular utility in the cleaning of painted and unpainted exterior aircraft surfaces and to a method for applying the cleaning composition to the exterior aircraft surfaces.
(2) Description of the Prior Art
There are many different types of cleaning compositions known in the art. U.S. Pat. Nos. 3,234,138 to Carroll, 3,240,715 to Foley, and 5,534,181 to Henkel et al. illustrate some of these compositions. The Carroll patent illustrates a detergent composition for cleaning hard surfaces. The detergent composition includes an inorganic phosphate component, an ethanolamide nonionic detergent component, a low molecular weight soap component and water. The Foley patent relates to a liquid detergent composition comprising a mixture of diethanolamides of higher fatty acids of 10-22 carbons containing hydroxy substituents, and at least 1% by weight based on the diethanolamides of dicarboxylic aliphatic acids of about 6-13 carbons and diethanolamide salts of higher monocarboxylic acids of 10-22 carbons containing hydroxy substituents. The Henkel et al. patent relates to a cleaning composition containing from about 0.4% to about 5.0% of an alkali metal salt, from about 0.3% to about 4.0% of a nonionic fatty acid amide, from about 0.3% to about 4% of an iso-fatty acid, from about 2% to about 7% of a builder, from about 1% to about 15% of a glycol ether, from about 1% to about 15% of a nonionic surfactant, and from about 50% to about 95% water.
Existing products used to clean the exterior of Navy aircraft are formulated with a solvent content of 10 to 15% and include other constituents that are cause for environmental concern. Propylene class glycol ether coupling solvents included in existing products to improve cleaning performance and thermal stability are volatile organic compounds (VOCs). Furthermore, glycol ether solvents typically have low permissible exposure limits (PELs) on the order of 100 ppm contributing to workplace health hazards.
A vapor phase corrosion inhibitor, morpholine, included in existing products to protect partially filled steel drums from corrosion at the liquid-vapor interface is also a VOC and listed as a hazardous air pollutant (HAP) by the 1990 Clean Air Act.
Finally, a typical surfactant component of the existing cleaners contains a phenoxyl group in the chemical structure. During biodegradation this is thought to produce phenol, a compound toxic to bacteria vital to the biodegradation process. This may result in waterway pollution and cause difficulty in waste treatment operations.